Researchers discover unusual competition between charge density wave and superconductivity

Phase of pressure temperature for CsV3 Sb 5. Credit: Yu and al.Prof. Chen Xianhui, University of Science and Technology of China of Chinese Academy of Sciences (CAS), led a research team that discovered an unusual competition between superconductivity and charge density wave (CDW). This was in CsV3 Sb 5, a layered kagome metallic, and provides important experimental evidence to understand novel CDW and superconductivity. This result was featured in Nature Communications.CDW and traditional superconductivity are two distinct electronic states. Both originate from Fermi instability and electron phonon coupling. The conventional coexistence image of superconductor and CDW shows that after entering CDW, the energy gap opens due to nesting Fermi surfaces. This results in the loss density of states which is indicative of CDW competing against superconductors.Increasing pressure or chemical doping can suppress CDW status. The superconducting critical temperature (Tc) will exhibit a single dome-like behavior if CDW status is suppressed. Because of the strong geometric frustration, new quantum states including superconducting states that are unconventional and chiral density wave types, can be predicted.A novel superconductor CsV3 Sb 5 with a layered cage structure was discovered recently. It has a CDW temperature of 94 K and a phase diagram under high pressure.They measured high voltage electric transport and magnetic susceptibility to find that T c behaves like a double dome when pressure is increased, instead of a single dome. The samples exhibit abnormal T c suppression and superconducting widening when the pressure is between 0.7 GPa to 2 GPa. The CDW becomes completely compressed when the pressure reaches 2 GPa. This is three times the normal pressure.An anomalous double-dome superconducting phase diagram could be due to the transition from a commensurate CDW status to a nearly commensurate CDW status. The results indicate that both the superconducting and CDW states of CsV3 Sb 5 are sensitive to pressure, with numerous pressure phase diagrams.This study also revealed the unusual competition between superconductivity & CDW in CsV3 Sb 5, which gives experimental clues to the unorthodox CDW mechanism.Learn more about Superconductivity and high critical temperature in 2D semimetal-tungsten nitrideF. H. Yu et al., Unusual competition for superconductivity & charge-density wave state in a compressed TOPO KAGOME metal, Nature Communications (2021). Information from Nature Communications F. H. Yu and colleagues, Unusual competition for superconductivity & charge-density wave state in a compressed TOPO KAGOME metal, (2021). DOI: 10.1038/s41467-23928-w